The present invention relates to a hydraulic fitting for connecting to a tube flare which has a tubular male plug that engages a flared surface with a radiused or rounded edge to form a line contact seal. The wall at the end of the male plug is of a cross section adjacent the rounded edge so the wall will resiliently deflect as the fitting is tightened to keep a load on the seal line during use to insure a tight seal.
In the prior art, threaded hydraulic couplers have been used for a long time. These include couplers with an internally threaded cap that surrounds a flared seat formed on a tube for carrying the hydraulic fluid, and a male plug which has external threads so the cap threads onto the male plug and as the parts are tightened the end of the male plug is forced onto the seat. The plug has an end edge that engages the seat for sealing. In many instances, the ends of the plug and the seats are manufactured to the same angle, so that they seat across a fairly large surface area that is used for providing the hydraulic seal for hydraulic fluid under pressure being carried through the line or interior passageway.
Leaks are a problem, and there is a need for a tight, leak free fitting that is easily connected without an excessive amount of threading pressure or coupling pressure, and which will maintain the seal for a long period of time.
The present invention relates to a threaded hydraulic coupling, which includes a male plug that is captured with a threaded female cap that surrounds a flared seat on a tube and which is formed to provide a positive, enduring seal. The tube flare is formed at a selected included angle from the central axis of the tube passageway. The cap is threaded onto the male plug. The male plug has an end edge portion that has a radiused outer surface, so that a line contact is made and maintained between the end of the plug and the flared seat surface. A line contact insures a leak-free, easily made seal.
The tubular wall at the end of the plug is controlled in cross-sectional size between the rounded end edge and the main body of the plug. The rounded edge will deflect inwardly as the fitting is tightened, to provide a resilient loading of the end edge of the plug that contacts the seat. As use occurs, there will be a load maintained on the sealing edge due to the resilient deflection between the end of the plug and the seat.
Two forms of the invention are shown. In one form the end portion is tapered to provide a reduced cross section for deflection. In a second form, an internal groove is provided to reduce the wall plug thickness so the end edge will resiliently deflect. The coupling is easily made, using standard manufacturing procedures, and by providing a line contact between the mating parts, it is insured that a tight seal is made. With the controlled cross section support wall to provide resilient loading of the seal, the seal is maintained for long periods of time.